The head of US intelligence was exposed on national television yesterday as being unaware of the arrests in Britain of suspects in an alleged terrorist plot.

James Clapper, director of national intelligence, looked stumped when asked by Diane Sawyer on ABC about the arrests of 12 suspects in London and elsewhere around Britain earlier this week. "London?", Clapper asked, looking puzzled.

Later, the White House admitted that Clapper had not known about the developments in the UK.

John Brennan, the White House adviser on homeland security and security, said; "Should he have been briefed by his staff on those arrests? Yes."

The show was taped on Monday but hours after the arrests, which received wide coverage on US television.

The gaffe could make life difficult for Clapper as the post of director of national intelligence, since its creation after the 9/11 attacks, has been a controversial one, seen as an extra agency in an already crowded field, and without real power. It was intended to co-ordinate the work of the dozen or so US intelligence agencies but has yet to establish serious credibility.

Clapper's job is to brief the president each morning on intelligence developments.

One explanation offered is that he was focused on North-South Korean tensions. Brennan, defending Clapper at a press conference, said: "I know there was attention by the media about these arrests and it was constantly on the news networks. I am glad that Jim Clapper is not sitting in front of the TV 24 hours a day and monitoring what is coming out of the media."